Testimony consists in imparting information without supplying evidence or argument to back one's claims. To what extent does testimony convey epistemic warrant? C. J. A. Coady argues, on Davidsonian grounds, that (1) most testimony is true, hence (2) most testimony supplies warrant sufficient for knowledge. I appeal to Grice's maxims to undermine Coady's argument and to show that the matter is more complicated and context-sensitive than is standardly recognized. Informative exchanges take place within networks of shared, tacit assumptions that affect the scope and strength of our claims, and the level of warrant required for their responsible assertion. The maxims explain why different levels of warrant are transferred in different contexts